The invention relates to conductor track structures on a nonconductive support material, especially fine conductor track structures, and a method for producing the conductor track structures
Through the article, "LAD--A novel, laser-supported coating process for fine conductor metallization" from No. 10, vol. 81 (1990), of the technical journal "Galvanotechnik," it has become known to apply Pd acetate from a solution as a thin film on the full surface of a nonconductive support material in order to produce fine conductor structures of definitely less than 100 mm. By subsequent exposure to laser light by means of an excimer laser with a wavelength of 248 nm in the area of the conductor structures that are to be produced, metal atoms are then released as nuclei for a subsequent nonelectrical metallization. Before the metallization, however, it is necessary to perform a rinse to remove the undecomposed areas of the metal-containing film applied to the support material. The quality of this rinse process plays a decisive part for the avoidance of wild growth problems in the subsequent nonelectrical metallization. Moreover it has been found that, by means of the method described it is not possible to achieve sufficient strength of adhesion of the deposited metal conductor tracks.
In DE 42 10 400 C1 a method is disclosed for the direct deposition of copper from a film of a mixture of heavy metal salts applied to a substrate by local heating by means of a laser. This method lies in the field of thermally activated chemistry, with the disadvantage that the fineness of the conductor track structures that can be achieved is limited. Furthermore, the applied film is an electrically conductive film, so that before the metallization a complicated and problematical rinsing process is necessary. The use of a nonconductive heavy metal complex and a cold break-up of the heavy metal complex by means of an excimer laser-UV radiation in order to split off the heavy metal atoms is neither disclosed nor suggested.
In DE 41 24 686 A1 there is described, among other things, a process in which a structured deposition of copper from a gas phase containing an organic copper-heavy metal complex is performed on a substrate by means of the action of laser radiation energy. The great disadvantage of this process is that the structured deposition of the copper takes place in a vacuum chamber with an inert gas atmosphere. The high cost of apparatus and technical labor is an obstacle to a wide use of this process in the area of conventional circuit boards and printed circuits.
U.S. Pat. No. 4,574,095 discloses a method in which a substrate is exposed in a vacuum chamber to the vapor of a palladium complex compound and is then irradiated through a window with a 249 nm excimer laser to produce a structure. Since the deposition of palladium takes place from a vapor phase in a vacuum chamber, this process also is so expensive that its use in the field of conventional circuit boards and printed circuits is not economical.